Stefan Seipel 2003 An Introduction into Virtual Reality Environments Stefan Seipel [email protected]Stefan Seipel 2003 What is Virtual Reality ? VR is a medium in terms of a collection of technical hardware (similar to telephone, TV, etc.) Technically defined: Stefan Seipel 2003 Definitions of Virtual Reality Coates (1992): Virtual Reality is electronic simulations of environments experienced via head mounted eye goggles and wired clothing enabling the end user to interact in realistic three-dimensional situations. Greenbaum (1992): Virtual Reality is an alternate world filled with computer-generated images that respond to human movements. These simulated environments are usually visited with the aid of an expensive data suit which features stereophonic video goggles and fiber-optic gloves. Krueger (1991): ….The term (virtual worlds) typically refers to three-dimensional realities implemented with stereo viewing goggles and reality gloves. Stefan Seipel 2003 What is Virtual Reality ? VR is a mediated environment which creates the sensation in a user of being present in a (physical) surrounding Defined in terms of human experience: Stefan Seipel 2003 Variables to define Virtual Reality Vividness (richness of an environments representation) • breadth (visibility, audibility, touch, smell) • depth (quality, fidelity) Interactivity (extend to which a user can modify form and content of a mediated environment) • speed (update rates, time lag) • mapping (text, speech, gestures, gaze, complex behavior patterns) Stefan Seipel 2003 Classification of Virtual Reality and other Media high high low Interactivity Vividness book 35mm film 3D IMAX TV pay-TV VR photo- graph tama- gotchi Jonathan Steuer phone video conferencing Sensorama
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VR is a medium in terms of a collection of technical hardware
(similar to telephone, TV, etc.)
Technically defined:
Stefan Seipel 2003
Definitions of Virtual Reality
Coates (1992):Virtual Reality is electronic simulations of environments experienced via headmounted eye goggles and wired clothing enabling the end user to interact in realistic three-dimensional situations.
Greenbaum (1992):Virtual Reality is an alternate world filled with computer-generated images that respondto human movements. These simulated environments are usually visited with the aid ofan expensive data suit which features stereophonic video goggles and fiber-optic gloves.
Krueger (1991):….The term (virtual worlds) typically refers to three-dimensional realities implemented with stereo viewing goggles and reality gloves.
Stefan Seipel 2003
What is Virtual Reality ?
VR is a mediated environment which creates the sensation in a user of being present in a (physical) surrounding
Defined in terms of human experience:
Stefan Seipel 2003
Variables to define Virtual Reality
Vividness(richness of an environments representation)
1961 Headsight System (Philco Corp.)HMD, head tracking, remote video camera, telepresence
1965 The Ultimate Display(Ivan Sutherland)Stereoscopic HMD, computer generated images, tracking, visually coupled system
1967 Grope (University of North Carolina)6 degree of freedom force feedback
1977 The Sayre Glove (Sandin, Sayre, DeFanti Univ. Illinois)Gesture recognition
1987 Virtual Cockpit (British Aerospace)head and hand tracking, eye tracking, 3d visuals, 3D audio, speech recognitionvibro tactile feedback
Stefan Seipel 2003
System Architecture in Virtual Environments
DisplayDevices
SensorDevices
Simulation ManagerScene GeneratorSimulation Loop
RenderEngine
SensorHandler
User
Scene DB
Stefan Seipel 2003
How Do We Perceive 3D ?
Stefan Seipel 2003
How Do We Perceive 3D ?
Visual depth cues:
a) monoscopic cuesrelative sizeinterposition and occlusionperspective distortionlighting and shadowstexture gradientmotion parallax
b) binocular (stereoscopic) cuesstereodisparityconvergence
Stefan Seipel 2003
How can we recreate 3D sensation ?
Providing visual cues:
a) monoscopic cuesrealistic rendering / lighting simulation
b) stereoscopic cues -> stereodisparitypresentation of appropriate view to each eye - time multiplexing of images- multiplexing with chromatic filters (anaglyph)- multiplexing with polarizer filters- providing two views simultaneously
Stefan Seipel 2003
Color Encoded Stereo Image Pair
Stefan Seipel 2003
Time Multiplexed Stereo Image Pair
V-Sync at 60 Hz
Addidional V-Sync at 120 Hz(enforced with sync. doubler)
1. Visual and Acoustic Realism of Objects• 3D effect• level of detail• specularity• color and texture
2. RealtimeResponse (approx. >15 Hz)
3. Natural Like Interaction Metaphors(many degrees of freedom input)
4. Peripherial Visual Stimuli
Stefan Seipel 2003
Types of Virtual Reality Environments
1. Immersive Virtual Environments• subjects are visually isolated from the real environment• virtual scene is responding to the subjects actions• subjects are unable to perform in the real environment
2. Semi-Immersive Virtual Environments• subjects can perform both in the real and virtual environment• subjects perceive a strong involvement into the VE• subjects may perform less in the real environment
3. Non-Immersive Virtual Environments• the three-dimensional scene is considered as a part of
the physical environment• subjects do fully respond in the real environment• relatively little involvement into the VE
Software Tools for Implementation of Virtual Environments
Stefan Seipel 2003
Concepts of Simulation Libraries(WorldToolkit , VRTK)
Scene Graph Representation• Scene is composed of nodes
• Node relationships are expressed in a hierarchical graph• A node contains geometries, attributes and transformation matrices
Simulation Loop with User Definable Callback Function• Behaviour is coded in callback function• Simulation state variables are used for dynamic control